Transport properties and magnetic disorder/order transition in Fe Ag100− films

We have studied the magnetic disorder/order transition in Fe x Ag 100-x films, with x varying from 10 to 30, focusing our attention on the interplay between transport and magnetic properties. The samples have been deposited by DC magnetron co-sputtering and analyzed by magneto-optic Kerr effect and magnetoresistance measurements, with external magnetic field applied both in and out of the film plane. Magnetization and magnetoresistive results indicate that for low Fe content (x<20) the system can be described as a granular isotropic superparamagnet. In the high concentration range (20<x≤30) the effect of local magnetic ordering emerges and the films can no longer be considered as granular. The presence of magnetic coherence on different length scales in this regime is discussed and related to coalescence of magnetic particles and clusters formation, with increasing Fe concentration above 20%. This value appears as a critical iron content around which the magnetic disorder/order transition occurs.